Chronic wounds represent a growing challenge in medical care.

Part 1: The aim of this part of the study was to collect wound swabs and to answer the question whether the rapid diagnostic tool using enzyme activities can display an infection prematurely. This means that an increased enzyme activity (especially MPO, NHE, LYS, gelatinase, pH) measured overed 3 days, would indicate a change in the wound bed (infection, Inflammation) earlier than the regularly performed clinical assessment.

Part 2: The aim of this part of the study was to evaluate (I) the possibility of wound fluid acquisition by means of an "additional collector" during ongoing NPWT and to answer if (II) this secretion can be biochemically analyzed for enzyme activities in order to be able to detect a change in the wound situation at an early stage.

The study is composed of two parts, which run independently of each other. However, in both parts the course of the wounds is analyzed.

Part 1: Two wound swabs are taken. One used for routinely performed microbiological analysis and the second will be used for biochemical analysis (enzyme activities). The aim of the wound swabs is to answer the question whether the rapid diagnostic tool used in the examination can display an infection prematurely or not. This means that an increased enzyme activity (especially MPO, NHE, LYS, gelatinase, pH) would indicate a change in the wound bed (infection, inflammation) earlier than the regular clinical assessment. These wound swabs are expected to function as an improvement of the biochemical assays or rather of the technology concerning sensitivity and specificity of, for example, the pH number, the MPO, the LYS, the gelatinase and the elastase. In addition to that, the correlation between the Enzyme activities and the course of the infection will be examined. This technology is supposed to be later used as an early infection diagnostic tool in wound fluids. The followup of this testing system is a crucial prerequisite for the application of the technology in VAC therapy (part 2).

Part 2: The findings of this examination will be used to investigate the applicability of the developed in-vitro early infection diagnostic tool in negative-pressure therapy (VAC therapy; vacuum assisted closure).

Patients of the plastic surgery with a NPWT are included in this prospective study. Before the NPWT will be applied, two swabs (biochemical and microbiological analysis) of the wounds will be taken. After installation of the dressing, the connecting tube between the wound and the vacuum-generating device will be cut and an "additional collector" will be inserted. This collector will be changed daily and afterwards the concentrations of enzymes (lysozyme, elastase, myeloperoxidase) will be biochemically analyzed.

Inclusion Criteria:

• signed informed consent
• older than 18 years old
• open wound of varying etiology
• VAC therapy (KCI) (part 2)

Exclusion Criteria:

• under 18 years old
• pregnant women
• less than three measurement data (less than three swabs) = part 1
• VAC-instill therapy = part 2

The cohort will be selected by inpatients with wounds (part 1) or with negative pressure wound therapy (part 2)

There is not a plan to make IPD available.